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Raw Oyster Pasteurization Cuts Viral Food Poisoning Risk

Apr 30, 2013 06:20 PM By Ashik Siddique

Eating raw oysters puts people with weak immune systems at risk of food poisoning from pathogens like Norovirus and Hepatitis A; a pasteurization method using electron-beam technology can increase the safety of raw shellfish consumption. Creative Commons

Raw oysters used to be a rare delicacy, but their increasing availability at gastropubs and eateries has led to a dramatic increase in the rates of shellfish food poisoning in recent years. A new study suggests that a technique called electron beam pasteurization can make the nutritious seafood safer to eat.

Although the marine bivalves are as safe for healthy consumers to eat as they have ever been, the growing popularity of raw oysters has put more Americans with weakened immune systems at risk for gastrointestinal illnesses related to noroviruses and bacteria like Vibrio vulnificus, according to a recent report from the Centers for Disease Control and Prevention (CDC).

Foodborne illnesses from shellfish consumption rose 43 percent from 2008 to 2012, and the CDC estimates that the virus infection risks from eating raw oysters may cost the United States as much as $200 million each year.

The Food and Drug Administration encourages people with weak immune systems to avoid raw oysters altogether. While existing processing methods like freezing, pressurization, and electron-beam irradiation can reduce the risk of contamination from raw shellfish, attempts to regulate such safety methods have been unevenly applied and opposed by major fishing industries.

Electron-beam irradiation has already been approved by the FDA for controlling the naturally occurring Vibrio vulnificusbacteria in shellfish, which can be fatal when eaten by people with diabetes, liver disease, and other conditions that weaken the immune system.

Now, researchers from Texas A&M University have released findings suggesting that the electron-beam pasteurization method can also control food poisoning from viruses, which are more difficult to treat than bacteria.

Their results will be published in the June issue of the journal, Applied and Environmental Microbiology, and are available online ahead of print.

"This is the first study that has attempted to quantify the reduction in infection risks of raw oysters contaminated with different levels of virus when pasteurized at FDA-approved doses," said microbiologist Dr. Suresh Pillai, senior author of the paper.

The study, led by toxicology graduate student Chandni Praveen, investigated the effects of electron-beam pasteurization on raw oysters contaminated with norovirus and hepatitis A viruses, which are common pathogens that can threaten shellfish eaters.

"Bivalves such as oysters are also filter feeders that obtain their food by pumping water through their system and filtering small organisms," Praveen said in the statement. "This can lead to the possible accumulation of [norovirus and hepatitis A] viral pathogens, as well as bacterial pathogens."

The results showed that a concentrated dose of energy reduced hepatitis A infection risk by 91 percent, and norovirus infection risk by 26 percent.

Electron-beam pasteurization is a relatively green technology which uses no chemicals, said Pillai. It uses commercial electricity to produce the ionizing radiation, which kills viruses and reduces infection risk without cooking the oysters.

No word on whether the technique alters the taste and texture of raw oysters, but Pillai recommends electron-beam technology as part of a comprehensive food safety plan to fight food poisoning, increase public health, and reduce medical expenses.